This study evaluates the effects of this novel 5HT3 antagonist on gastrointestinal transit and rectal sensation and compliance in patients with irritable bowel syndrome. We anticipate these data will be used in the coming year to complete two pivotal studies for FDA approval of this medication for treatment of IBS. The pharmacodynamic data prove the importance of the 5HT3 control of colonic motor and sensory function in disease, a concept which was extensively studied in healthy controls in previous Mayo GCRC studies.